This invention relates to a multiblade plastic fan for automotive vehicle and more particularly to a transverse cross section of the blades contoured to provide a better life or strength of the blades while maintaining a favorable deformation of blade configuration to an increasing degree with an increase in rotational speed of the fan.
It has been proposed to manufacture the cooling fans from molded plastics on account of prevention of noises occasionally produced by metal blades and simplicity of the deformation of blade configuration mentioned above to thereby substantially reduce the air flow and the horsepower requirement in order to avoid any tendency of over-cooling and hence a reduction of operating efficiency of the engine.
Difficulties were encountered in making the thickness of the fan blade to a suitable value in that, the blade tends to be collapsed during the service life at a portion in the leading side of the blade. This may be attributed to a load caused by resonance of the blade and the driving member of engine to be concentrated particularly to that location.
The employment of the known fluid coupling between the driving member and a hub of the fan has resulted in a favorable damping action of the fluid effective to prevent the fan blade from the aforementioned resonance, being unable however to be effective when there is a situation in which the known fluid chamber of the coupling is emptied of its contents fluid in response to an environmental occasional temperature variation.
Mere selection of thickness of the blade at the aforementioned portion in the leading edge may result in a favorable counter measure for above mentioned conventional drawbacks. On the other hand, however, it will apparently be encountered with another difficulty in ensuring the ability of deforming the blade configuration positively in the desire optimum sense at higher operational speeds of the fan, so as to provide a nearly ideal performance thereof, without overcooling the engine.